The present invention relates to a reinforced member which is made from a steel product having a strain aging characteristic and has a closed section in the direction perpendicular to the axis of the reinforced member, and more particularly to a reinforced member constructing a vehicle structural member such as a member and a roof rail.
There have been proposed various steel products having a strain aging characteristic, in order to ensure a desired strength of structural members while decreasing a vehicle weight by decreasing a thickness of a steel product. For example, Japanese Published Patent Application Nos. 2001-303185 (≈U.S. Pat. No. 6,692,584) and 2001-335889 disclose typical steel sheets having a strain aging characteristic.